Container for asphalt



Patented July 14, 1936 UNITED STATES PATENT OFFIQE No Drawing. Application July 8, 1932, Serial No. 621,527. In Great Britain July 23, 1931 8 Claims.

This invention concerns metal containers such as barrels, drums or the like for holding asphalt, under which expression is included all those solid, semi-solid or plastic bituminous substances, such as asphalt, bitumen, tar or pitch, whether derived from naturally occurring deposits or obtained artificially by the distillation, evaporation or concentration of crude petroleum, coal tar or the like materials, or from derivatives thereof, and which by virtue of their chemical or physical properties have a tendency to adhere to the surfaces of metals.

When required for use the asphalt is separated by stripping by means of a physical operation and without the application of heat, from the container.

For the purpose of preventing the adhesion of asphalt to the metal surfaces of its container it has been proposed to provide the inner surfaces of the containers with coatings of clay, lime or similar material so that such coatings can readily be detached from the metal surfaces when the asphalt is stripped therefrom. Such coatings are not entirely satisfactory because they possess little mechanical strength and if cracked or broken during the handling or transport of the container such cracks enable the asphalt to penetrate through to the metal and adhere thereto. Again, the coatings remain for the most part attached to the surfaces of the detached asphalt and thereby spoil its appearance and being foreign to its nature may impair its subsequent utilization in the industry.

The present invention has as its object to avoid such disadvantages and provides an improved method of treating the interior surfaces of such metal containers previous to the introduction of the asphalt therein, whereby the natural adhesive tendency of the asphalt for the surface of the metal is considerably lessened or removed, and the subsequent separation of the one from the other by the application of mechanical force is greatly facilitated.

According to the invention the improved method of treating the interior surfaces of metal containers destined to contain asphalts so as to render such surfaces non-adherent to or easily separable by physical force from the asphalts consists in applying to the interior surfaces having or provided with films or coatings of metal oxides, (in the case of iron or steel containers fiIms or coatings of magnetic or black oxide of iron or of admixtures of such oxide and ferric oxlde,-or of ordinary rust) liquid or semi-liquid reagents which .act to loosen the films, or coat-l ings rendering their detachment when stripping the asphalts from the interior surfaces a simple operation.

The liquid or semi-liquid reagent, while rendering the film or coating readily detachable, preferably has also one or more of the following properties:-

(a) of reacting chemically with the metal of the container so as to generate at once or subsequently bubbles of hydrogen.

(b) of reacting chemically with the metal of the container while having less action upon any film or coating pre-existent on the surface of the said metal, or upon any film or coating formed or engendered at once or subsequently by its own chemical reaction with the said metal, so as to render the said film easily detachable.

(c) of producing by chemical interaction of its own components, substances having the aforesaid properties (a) and (b).

(d) of forming or depositing upon the interior surface of such metal container a film or coating which is hygroscopic.

In an embodiment of the invention use is made of the fact that the surfaces of the iron or steel which is commonly used to construct the metal containers have acquired thin films or coatings of magnetic oxide of iron, this being more particularly the case when the containers or the metal used in constructing them have or has been 1 subjected to the action of heat such as that employed in welding the seams and joints during the process of manufacture. The interior surfaces of such iron or steel containers may also be covered wholly or in part with ordinary rust in addition to the aforesaid magnetic oxide. If the surfaces do not possess films or coatings of either oxide, they may be subjected to heat treatment to form the coating of black oxide, or allowed to become rusty by exposure to the atmosphere, or by other appropriate means. It is convenient, however, to utilize the coating of black oxide rather than that of ordinary rust, since the former more nearly approaches the natural colour of asphalt and therefore detracts less from the subsequent appearance of the latter when removed from its container.

The coating of oxide may also be applied to the interior surface of the container in the form of a paintor wash, or the oxide may be suspended in the reagent or produced by chemical reaction between the latter and the metal of the container.

The film of iron oxide is not usually continuous or unbroken over the surface of the conof such film detachable by chemical reaction with the metal underlying the said film; it may provide further means for preventing or diminishing the adherence of the asphalt and for this purpose the reagent is chosen so that by its reaction with the said underlying metal bubbles of hydrogen are generated which not only assist in making the oxide film detachable but also in themselves constitute a layeror film to which neither metal nor asphalt will readily adhere.

' The reagent may be a solution of an organic or inorganic acid so chosen that either because of its nature or state of concentration its chemical reaction with the metal of the container is soon exhausted or inhibited, or else it forms by such reaction a protectivecoating inhibitory to continuous reaction with the metal.

Instead of an acid a solution of an acid salt may be used or a solution of an acid with a salt or again a combination of two or more chemical substances may be used which by interaction between themselves and the metal of the container, or with the oxide existent on or applied to the surface of the latter, produce the substances necessary for procuring the desired result. 7

In order to ensure still further the'non-adherence of the asphalt to the metal the reagent may be hygroscopic in character so that by attracting moisture from the atmosphere it provides the film of water which is necessary for promoting the chemical reaction, and which in itself has little adherence to the asphalt or metal and thus assists in making the method efiective.

As examples of reagents or combinations of reagents suitable for carrying out the invention the following have been found tobe effective:-

1. Example embodying the use of an organic acid Grams Oxalic acid 10 Crude glycerine 10 Water 100 The'use of the glycerine in this formula is to ensure the presence of a hygroscopic film and impede the evaporation of the water when warm asphalt is poured into the container.

2. Example embodying the use of an acid, which while acting on the metal and generating bubbles of gas eventually forms a:,compound with the metal which inhibits further action 'Grams Orthophosphoric acid '8 Glycerine 10 Water 100 3. Example embodying the use of an acid salt Grams Sodium dihydrogen phosphate '7 Crude glycerine 9 Water 100 4. Example embodying the use of a combination of an acid with a salt Grams Orthophosphoric acid 3.2 Calcium chloride 17 Water 100 reactions to suit the condition or composition of I the metal container, and the asphalt it is destined to receive.

It will also be noted that the salts given by way of example are hygroscopic by nature and by so proportioning the quantities of acid and salt that an excess of the latter remains in the film above that required completely to react with the acid provision can be made for procuring a hygroscopic film on the metal.

5. Example embodying the use of a solution forming or depositing a film or coating which is hygroscopic r V Grams Calcium chloride 20 Water 100 Instead of calcium chloride calcium nitrate may be used.

The reagent prepared according to one or other of the aforesaid examples may be distributed by spraying or painting or by any other convenient means, over the interior surface of a steel or iron container, and after allowing sufficient time for the chemical reactions to be verified and while the film upon such surface is still moist the container may be filled with asphalt which has been previously melted. About 100 cc. of the aforesaid reagents are required fora drum holding approximately 35 gallons of asphalt. It is important for the successful carrying out of the invention that the temperature of the asphalt be not high enough to drive oil the water contained in the applied film, but this condition is in practice secured automatically since the qualities of the asphalt are impaired by heating for long to a temperature much above their melting points. The lid may be similarly treated and then secured in position. 7 7

Moreover, the softer and more adhesive varieties of asphalt have usually a low melting point, Whichis below the boiling points'of the liquid reagents employed in carrying out the invention.

Should, however, it be necessary to utilize the invention for asphalt melting at an unusually high temperature, the purposes of the invention may still be secured by increasing the concentration of the salts or by employing reagents which embody substantial proportions of glycerine. When the asphalt has cooled to the temperature of the atmosphere it will be found that it has little or no adherence to the metal surface of the container and that the latter can .be easily removed or stripped by the method customary in the industry.

Since it iswell known that both, the iron or steel of the metal container and the asphalt it is destined to receive are subject to variations in nature and composition preliminary experiments may be required to determine the most suitable reagent and the proportions of its ingredients.

As a further precaution to avoid undue corrosion of the metal container by the reagents utilized or by the substances produced by the chemical reaction it is advantageous to include in the liquid solution used for treating the metal surfaces substances acting as inhibitors such as colloids for instance glue, gelatine, casein or the like. It may be pointed out, however, that in the examples hereinbefore referred to wherein phosphoric acid is included as an active reagent, the latter may render unnecessary the use of an inhibitor owing to its well known property of re.- acting with the surface of iron or steel and forming a protective coating or film of phosphate of iron upon such surface. The production of such a film of iron phosphate as one of the products of the chemical reaction is of particular advan tage in carrying out the process since it may act as a substitute for the naturally occurring film of oxide of iron in case the latter should be absent from the surface of the metal, and like it may be made detachable from the underlying surface by the chemical reactions as above explained.

It will be understood that the reagent when applied to the inner surfaces of the container is still to be in the moist state when the asphalt is introduced therein. If the reagent includes a hygroscopic material the containers may be left standing for some while but otherwise the asphalt should be filled in before the reagent has had time to dry.

What I claim is:

1. In the art of filling steel containers with asphalt the steps of providing a film of oxide of iron, then applying a liquid containing an acid A asphalt the steps of providing a film of oxide of iron, then applying an aqueous solution of an acid acting salt to loosen the said oxide film and thereafter filling said container with asphalt while said oxide film is in a loosened state.

3. In the art of filling steel containers with asphalt the steps of providing on the interior surface of the container a film of oxide of iron, then applying a liquid mixture containing an acid acting reagent together with an inhibitor and thereafter filling said container with asphalt while said oxide film is in a loosened state.

4. In the art of filling steel containers with asphalt the steps of providing on the interior of said container a film of oxide of iron, then applying a mixture containing a liquid acid acting reagent and a hygroscopic salt and thereafter filling said container with asphalt while said oxide film is in a loosened state.

5. In the art of filling steel containers with asphalt the steps of providing on the interior surface of said container a film of oxide of iron, then applying an aqueous solution containing oxalic acid, to loosen the said oxide film and thereafter filling said container with asphalt while said oxide film is in a loosened state.

6. In the art of filling steel containers with asphalt the steps of providing on the interior surface of said container a film of oxide of iron, then applying an aqueous solution containing orthophosphoric acid to loosen the said oxide film and thereafter filling said container with asphalt while said oxide film is in a loosened state.

'7. In the art of filling steel containers with asphalt the steps of providing on the interior surface of said container at film consisting of an oxide of iron, then applying an aqueous solution containing di-hydrogen phosphate to loosen the oxide film and thereafter filling said container with asphalt While said oxide film is in a loosened state.

8. In the art of filling steel containers with asphalt the steps of providing on the interior surface of said container a film of oxide of iron, then applying an aqueous solution made up from orthophosphoric acid and calcium chloride to loosen the. oxide film and thereafter filling said containers with asphalt while said oxide film is in a loosened state.

JAMES MCCONNELL SANDERS. 

